Instituto de Producción Animal, Facultad de Agronomía, Universidad Central de Venezuela, Maracay, Venezuela.
Departamento de Fisiología, Facultad de Veterinaria, Universidad de la Republica, Lasplaces 1550, Montevideo 11600, Uruguay.
Physiol Behav. 2019 May 15;204:324-335. doi: 10.1016/j.physbeh.2019.03.011. Epub 2019 Mar 13.
The aim of this study was to compare circadian rhythms of serum cortisol and insulin concentrations, glycemia, glycemia:insulin ratio (GLY:INS), rectal, vaginal and surface (ST) temperatures as well behavioral patterns during the follicular (FOL) and luteal (LUT) phases in ewes. All the variables were measured during both phases of the estrous cycle in 8 West African ewes during a 24 h period. Cortisol concentrations were greater during FOL than LUT (30.9 ± 2.1 ng mL vs 24.1 ± 2.1 ng mL; P < 0.01); cosinor analysis revealed also differences in the circadian pattern: while the acrophase of the cortisol secretion during the FOL occurred at 10:00 ± 0:49 h, coinciding with higher environmental temperatures during the LUT was observed at 05:07 ± 0:49 h (P < 0.05). There were no differences in insulin concentrations according to the phase of the estrous cycle (FOL: 43.3 ± 6.6 μg mL vs LUT: 44.9 ± 6.6 μg mL); however, insulin secretion varied according to the time of the day (P < 0.01) and showed a strong robustness in both phases of the estrous cycle (>40%), with acrophase occurring at sunset. Glycemia was greater during the FOL than the LUT (69.9 ± 1.1 mg dL vs 63.9 ± 1.1 mg dL, respectively; P < 0.01), and varied according to the time of the day (P < 0.05), without interaction between both effects. However, the strength of rhythmicity was <40% during both phases. GLY:INS ratio was greater in FOL than LUT (2.2 ± 0.2 vs 1.8 ± 0.2, respectively; P = 0.04), indicating that the greater glycemia observed during FOL did not trigger the same secretion of INS than during LUT. Rectal and vaginal temperatures, as well as nasal vein, front and neck ST were greater during FOL than during LUT (P < 0.05). There was no circadian rhythm for vaginal temperature but, both rectal temperature and the mean surface temperature showed a strong robustness (>65%). The mesor of the rectal temperature was greater during the FOL than during the LUT (39.2 ± 0.1 °C vs 38.8 ± 0.1 °C, respectively; P < 0.05). Ewes were observed urinating more times during the FOL than during the LUT (7.3 ± 1.5% vs 1.7 ± 1.5%, respectively, P < 0.05). Ewes were observed standing, drinking water and in bipedal position more times during FOL than during the LUT (P = 0.07, P = 0.08 and P = 0.07, respectively). In conclusion, the phase of the estrous cycle affected the secretion and the circadian rhythm of cortisol and in consequence the metabolic activity, thermoregulatory response and behavior pattern in ewes.
本研究旨在比较绵羊发情周期卵泡期（FOL）和黄体期（LUT）血清皮质醇和胰岛素浓度、血糖、血糖：胰岛素比值（GLY:INS）、直肠、阴道和体表（ST）温度以及行为模式的昼夜节律。在发情周期的 24 小时内，对 8 只西非绵羊进行了测量。皮质醇浓度在 FOL 期高于 LUT 期（30.9±2.1ng/ml 比 24.1±2.1ng/ml；P<0.01）； 余弦分析还揭示了昼夜节律模式的差异：虽然 FOL 期皮质醇分泌的峰相位发生在 10:00±0:49h，但 LUT 期与环境温度较高时的峰相位发生在 05:07±0:49h（P<0.05）。 胰岛素浓度不受发情周期阶段的影响（FOL：43.3±6.6μg/ml 比 LUT：44.9±6.6μg/ml）； 然而，胰岛素分泌随时间变化（P<0.01），并且在发情周期的两个阶段都具有很强的稳健性（>40%），峰相位出现在日落时。FOL 期的血糖高于 LUT 期（69.9±1.1mg/dL 比 63.9±1.1mg/dL；P<0.01），且随时间变化（P<0.05），但两者之间没有相互作用。 然而，在两个阶段，节律性的强度均<40%。FOL 期的 GLY:INS 比值高于 LUT 期（2.2±0.2 比 1.8±0.2；P=0.04），表明 FOL 期观察到的较高血糖并未引发与 LUT 期相同的 INS 分泌。直肠和阴道温度以及鼻静脉、前颈和颈部 ST 在 FOL 期高于 LUT 期（P<0.05）。阴道温度没有昼夜节律，但直肠温度和平均体表温度具有很强的稳健性（>65%）。FOL 期直肠温度的中值高于 LUT 期（39.2±0.1°C 比 38.8±0.1°C；P<0.05）。与 LUT 期相比，FOL 期母羊排尿次数更多（7.3±1.5%比 1.7±1.5%；P<0.05）。与 LUT 期相比，FOL 期母羊站立、饮水和双足站立的次数更多（P=0.07、P=0.08 和 P=0.07）。 总之，发情周期阶段影响了绵羊皮质醇的分泌和昼夜节律，进而影响了代谢活动、体温调节反应和行为模式。
